I've made two hakamas myself some years back. No pattern - just a measuring stick and somebody elses hakama as a template. Took some math work since the dimensions for fabric I could buy differed from what was used on the original.

It was okay and a lot cheaper than buying one of those insanely expensive hakamas from the shops. However I wouldn't do it again.

BTW: for material inside the Koshita I used old vinyl samples. I tried first to dip them in boiling water thought to make sure they could survive washing.

Also remember to wash the fabric before sewing the hakama. I forgot that on the first one I made, and it turned out to short for me.